The present invention relates to methods and devices for minimizing band spreading caused by long tubing runs between a separation column or cartridge and a detector. Chemical analysis is a process in which the presence and/or quantity of a composition is determined. Chromatography is a process in which compositions are separated from each other, often used in chemical analysis. Typically, samples are in the form of a solution holding one or more compositions. A pump creates a flow of fluid. Samples are placed into this flow of fluid by a sample injector. The sample is carried by the flow of fluid through tubing to a column or cartridge. The cartridge or column is packed with a solid phase media. The different compounds held in the sample exhibit different affinities for the solid phase material and separate from each other. The flow from the column is received by a detector. The detector produces a signal that changes as the properties of the fluid changes takes place over time due to the separation of the compounds. These changes are recorded as peaks or bands and are indicative of a particular composition.
The separation of compound by the column or cartridge is reversible. The compositions leaving the solid phase media are able to redistribute and mix with the surrounding fluid. This redistribution of the concentrated compositions is known as band spreading. Band spreading is undesirable in that it tends to obscure compositions that are present in small concentrations.
Columns and cartridges are often contained in an assembly with sample injector functions and pumping functions. The assembly allows the environment of the column and cartridge to be controlled. The column and/or cartridge communicate with one or more detectors through runs of tubing. The long runs of tubing promote band spreading.
Placement of the column and/or cartridge in close proximity to the detector is difficult. The column or cartridge is then subjected to changes in temperature which may lead to shifts in peaks. Moving the column and/or cartridge to the detector, away from the sample injector, may cause mixing of the samples with each other.